Re: ASLR revisited
Greetings, John Selbie! > For my open source project, I publish source code for Unix written in C++. > And as a convenience, I publish Win32 binaries compiled with Cygwin's g++ > build. I bundled the compiled EXE along with the dependent Cygwin DLLs > (cygcrypto, cyggcc, cycstdc++, cygwin1, and cygz.dll). > Someone rang me up today and said, "We're about to go live with your > pre-compiled binaries for Windows, but our compliance testing detected your > code isn't using ASLR (Address Space Layout Randomization). Can you fix?" > A quick internet search reveals that Cygwin has a compatibility issue with > ASRL. Process Explorer from sysinternals.com reveals that the process runs > without ASLR. As far as I recall, POSIX forking semantics are incompatible with ASLR. So, if my memory serves me well, the answer is "don't do that, your application will break badly." > Is there a workaround for allowing Cygwin code to have ASLR? I don't need > the fork() function. Build your application for native API. That's the only right answer. -- With best regards, Andrey Repin Wednesday, March 4, 2020 22:09:21 Sorry for my terrible english... -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
Re: ASLR revisited
On 3/2/20, John Selbie wrote:
> And I just discovered that recompiling with this added to the g++ command
> line:
>
> -Xlinker --dynamicbase
>
> Seems to work. Or at the least, triggers the process to show up in Process
> Explorer as ASLR?
>
> Good idea to continue with this?
I haven't looked at this in ages, but for gcc I use
LDFLAGS="${LDFLAGS} -Wl,--nxcompat"
# https://en.wikipedia.org/wiki/Data_Execution_Prevention
# Enable DEP with -Wl,--nxcompat
LDFLAGS="${LDFLAGS} -Wl,--dynamicbase,--export-all-symbols"
# https://en.wikipedia.org/wiki/Address_space_layout_randomization
#
https://stackoverflow.com/questions/24283918/how-can-i-enable-aslr-dep-and-safeseh-on-an-exe-in-codeblocks-using-mingw
# ASLR with gcc has a problem: -Wl,--dynamicbase doesn't emit the
necessary relocation table.
# As a workaround, you can pass -Wl,--dynamicbase,--export-all-symbols
Regards,
Lee
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Re: ASLR revisited
And I just discovered that recompiling with this added to the g++ command line: -Xlinker --dynamicbase Seems to work. Or at the least, triggers the process to show up in Process Explorer as ASLR? Good idea to continue with this? On Mon, Mar 2, 2020 at 8:26 PM John Selbie wrote: > For my open source project, I publish source code for Unix written in C++. > And as a convenience, I publish Win32 binaries compiled with Cygwin's g++ > build. I bundled the compiled EXE along with the dependent Cygwin DLLs > (cygcrypto, cyggcc, cycstdc++, cygwin1, and cygz.dll). > > Someone rang me up today and said, "We're about to go live with your > pre-compiled binaries for Windows, but our compliance testing detected your > code isn't using ASLR (Address Space Layout Randomization). Can you fix?" > > A quick internet search reveals that Cygwin has a compatibility issue with > ASRL. Process Explorer from sysinternals.com reveals that the process > runs without ASLR. > > I tried using the Windows 10 Exploit Protection Panel - and specifying an > exception for this executable to have mandatory ASLR. That results in the > code no longer running. Although the alternate option of "Botton-up ASLR" > did allow the code to run, but Process Explorer still doesn't show it > running with ASLR. > > Is there a workaround for allowing Cygwin code to have ASLR? I don't need > the fork() function. > > Thanks, > jrs > -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
ASLR revisited
For my open source project, I publish source code for Unix written in C++. And as a convenience, I publish Win32 binaries compiled with Cygwin's g++ build. I bundled the compiled EXE along with the dependent Cygwin DLLs (cygcrypto, cyggcc, cycstdc++, cygwin1, and cygz.dll). Someone rang me up today and said, "We're about to go live with your pre-compiled binaries for Windows, but our compliance testing detected your code isn't using ASLR (Address Space Layout Randomization). Can you fix?" A quick internet search reveals that Cygwin has a compatibility issue with ASRL. Process Explorer from sysinternals.com reveals that the process runs without ASLR. I tried using the Windows 10 Exploit Protection Panel - and specifying an exception for this executable to have mandatory ASLR. That results in the code no longer running. Although the alternate option of "Botton-up ASLR" did allow the code to run, but Process Explorer still doesn't show it running with ASLR. Is there a workaround for allowing Cygwin code to have ASLR? I don't need the fork() function. Thanks, jrs -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
